Tapping head



Jan- 30,y 194.5- s. B. HELLsTRoM TAPPING HEAD Filed Sept, 5, 1941 v@sheets-sheet 2 INVENTOR yep ,BZ HeZZJF/v/n.

l ATTORN s.

Jan. 30, 1945.

S. B. HELLSTROM TAPPING HEAD Filed sepit. 5, 1941 6 Sheets-Sheet' 5 Jan.4 30, 1945. l s. xaHELLs-rRoMl 2,368,359

TAPPING` HEAD ATTOR Ys.`

Patented Jan'. 30, 1945 l UNITEDk s'rlrrl-:sv rATENT ori-*ica asaltann TAPIING HEAD Sven B; Hellstrom, GrossePonte -Farms,-Mich., assgnorto Detroit Tap & Tool Company,` lD'etroit, Mich., a c orporationofy Delaware. n l Application september 5, 194i, sensi No. 4095er s claims.

The present invention relates generally toi apparatus for cutting screw threads interiorly wof holes or openings. While the primary object of the vpresent invention is to provide a simple, compactgrugged, and precise tapping head construction primarily intended for use as' an' attachment for 'a drill press or turret lathe, it will become readily ap'- parent from the following descriptionthatmany of the novel features of the present construction are especially suited to tapping machines Agenerally,` irrespective of whether theser novel features are'incorporated in Va unitary tappingihead construction or in a machine `designed "solely for thread tappingoperationsw The primary-object of the present invention is to provide a tapping head'constructiori in'which the feed of the tap, both to andfrorn the work, is accurately and precisely controlled by means of a lead screw in order Yto eliminate, insofar as is possible, errors in the` thread cutting operation.

Still further, the present invention contemplates the provision of substantially automatic means for controllingv the depth of cut of the tap together with means -for automatically reversing the directiony of lrotation of the tap spindle when a predetermined ldepth is reached.

VStill further, thelinvention contemplates the provision of simple', convenient and'easily adinstable electrical control mechani'smffor accurately and automatically controlling the feedof the tap spindle both to and from the work.V

StillA another object of the-present invention vconsists in the provision of'a novel and improved electrical control mechanism. This novel electrical control mechanism makes possible 'the simultaneous operation of a plurality of tapping machines or a plurality of tapping heads in such a way that a plurality of holes may be simultaneously tapped. The improved control system of the present invention is sufficiently flexible in its operation so that the plurality of holes being simultaneously tapped may be of different depth, may have different pitch threads, and yet'at the same time all holes may be simultaneously tapped and each individual tap will cut the proper threads to the proper depth,automatically reverse and return to its initial position entirely independently of the operationof the other taps.

Still another important feature of the present invention contemplates the provision of a tapping head construction which is compact and adaptable asa unit-. to adrill press, turret latheyor similar machine tool r`and in which thefeed of the vspindle is controlled by a lead screw located closely adjacent the'tap itself, thereby materially decreasing errors due to wind-up in the tap spindle and at the Ysame Atime greatly increasing the accessibility of the lead'screw in order to facilitate changes thereof when changes of taps ,are made.: e. y., e

An' important featureof the present invention resides in the provision of means' for drivingly interconnectingthe source of' power withthe' tap spindle in such a' manner as tojeliminate any axial thrust on the tap or tap spindle in order to establish a driving engagement vbetween vthe source of power and the tap'spindle.

Still another feature ofthe present "invention consists in the provision of a tapping machine or tapping head construction inwhich the tal? spindle is not yonly accurately and precisely controlled by means "of a lead screw but in 'which the tap and' tap spindle are rotatedA only' at such timesv as thev tap is actuallyentering or 'leavingth'e Work.I Y l i i Many other and further objects, advantages, and'features of the present invention vl i1lbe come moreclearly apparent from the following specification when c onsideredvinconnectionwwith 'the accompanying drawings forming a part thereof. y the drawings: l u Figure 1 is a Mfront elevational viewof a tapping head designed and intended for use as attachment to adrillpress or similar vpiecejof equipment ,v Y. Figure'z is a side elevationalvlew of 'the specic form of tappingihead construction illustrated inFigure, 1. i Y Figurey 3 is a transverse, sectional view taken substantially along the lines 3-3of ,Figure 2, lookingupwardly 'toward'the 'tapping head construction in the direction indicated Vloll thev arrows; -Figure 4 is a transverse,` sectional viewtaken substantiallyalong the line .4l-4 of Figure' 1, illustrating .the internal construction and arrangement of. parts. A

Figure 5. is a.` top ,p1an.fvievv`, taken along. the

une 5 5 if Figure 2, mpking' downwardly from the upper end of the-tappingheadconstruction. Figure 6 is a vertical, axial, sectional view taken substantially'along the line 6-6 of Figu'reA, illustrating in detail the internal construction. and arrangement ofparts;y r

Figure 7 isV a fragmentary,1' front elevational view -of a modified? formv of the present invennonfi11u'stfanng1s fornipf the invention particularly adaptable for use in-dep' hol'e tapping.' fr i Figure 8 is a transverse, sectional View taken substantially on the line 8 8 of Figure 7.

Figure 9 is avertical, sectional view with parts broken away showing in detail the modified form oi the invention disclosed in Figures 'l and 8.

Figure 10 is a fragmentary, side elevational View of the switch control mechanism, illustrating in detail the manner in which the feed ccntrol of the:tapping-lfieadoperates.v

Figure .11 is a circuit diagram illustrating one manner in which a plurality of tapping heads or tapping machines may be simultaneously corrtrolled.

Figure 12 is a side, elevational View similar -to Figure l, illustrating in further detail the'operation of the control mechanism. t

nalled thereon intermediate its ends a collar pinion 4|. This shaft 40 and the collar gear 4| are journalled for rotation in a suitable roller bearing assembly 42 and, as is clearly seen in Figure 6, are mounted for rotation on an axis which coincides with the axis of the rotation of the shaft |8. The extreme upper end of the shaft 49 is of reduced diameter and is journalied in a second series of roller bearings43 mounted within the hol-low lower end of the shaft I8.' As' is seen best in Figure 4 of the drawings, the collar pinion 4| 'mesheswith an idler pinion 45 journalled for rotation on a suitable sha-ft 4E, the pinion 45 being in 'meshing engagement with the gear 39 on the Figure 13 is a side, elevational view similar to Figures 1 and 12, illustrating the control mechanism in still further detail'. i

With more particular reference to thedrawings,it will be readily appreciated that only one specicjembodimentof the invention has been illustrated andI described inv detail and it 'will' be likewise appreciated rthat' many andvarious modifications of thisspecicform ofthe invention may be `made as circumstances requirewithout departing from the generic spirit of the invention jas set'forth in the subjoined claims.

1Wi'th` mere"4 particular Vreference to the "drawings, 'theunitary tapping headjconstruction disclosed 'comprises an adapter collar |0 which is siotted at 'l l; amrl providedl witnboss'es l2 'which 'are at' eianietricaiiyoppositesides. suitabiemachine screws`|'3"extend"through the bosses I2 and may be tightendupto lock'the tapping head cons ru'tib'nsfas a "whole in predetermined position uupon adrill'press or 'other suitable apparatus.

. -Ihe'(follar, I0'i`s` 'suitably'attached to a second 'ciiar or earing'nousig'cap f5 which in turn is securelyA fastened to theupper portion 'I6 of the mainhousingof the tappinghead.l The collar I5 has mounted therein an' annular oil' seal 'j I l "of "cont"entinal construction'which seri/'es to su'rroillfld the main l"drive" shaft B. The `main drive shaftfl B'Lfi's'lfprdvided with a "conventional taper ."siianl IYS! exteiiis axially ul)- wardly withinr the collar rreiribers I5. and I0. This shaft |9 is journalled` for rotation in an; annular series, @mail bearings Plfmoiihted una raceway 2|V .carried by the upper'por- -tion. .olf the 'main' housing, I6. MThe opposite raceway 22 forthel ball'bearings` 20 is'firrrilyanchored to the shaft |.8 by means of"a"suitabl`e lock'f'nut`23, thisv construction v'all being clearly illustrated `Figure" 6 Yof the drawings.'

Integrally formed on the lower'e'ndof the shaft I8 yis a'gear25 which' on its vlower axial face is provided with a Vseries 'of clutch teetlr26, the purpose andfunction of' which will be moreclearly described hereinafter. y

The `lower half'30' of the mainhousingi'of the tapping head construction is bolted to the` upper half "Iiof the -housing by 'means'r'of an annular series c-f bolts 3|. A suitable "counter-shaft'35 is" mountedl the housing on Aari-"axis parallel to the shaft' I8'. This@countershaft-provides means for -journalling /a-"gar clusterBGi/'onsuitable sets of rieedlelbearingsil" in order' that the gear clusterl36 willdoe freely rotatableon an axis parallel to the axisof the shaftIIf.. vThefv gear cluster 36 comprises upper and lowergears and 39, the upper gear 38- being infmeshing engagement-with .theggearfgwhich5 as hasbeendescribed above, isj integrally fconnetedrto the lowepend ofthe' feo shaft is. -An intermediate f s hartfanhas jour- .15

1 --lower endo-f the; gear cluster 35. The upper axial facefof 'thefcol-larlpinion 4 |v is provided with clutch teeth 4l,-.the.purpose and function of which will hereinafter become clear.

The upper portion of the shaft 4U is provided with .axially extending splines 48 which serve to mount -a clutch collar 49 which. has the upper and lower axial faces thereof provided with clutch teeth 50 and 5|', respectively, 4an'dit will rbe clear that the `mounting of this collaron"the shaft by meansv of the splines 48 serves 'to permit free axial shifting ofthe collar without disturbing the driving engagement between the collar 49 'and the shaft' 40. It will further be Seen that the clutch teethl are adaptedto drivingly engagewith the 'clutch teeth 26`when 'the collar-is shiftedr upwardly and 'the 'clutch teeth '5| are adapted to. drivingly engage with'the clutch-.teeth `4`| "when 'the collar isfsliifted downwardly. Itis likewise clear byA reference'to Figure At that the Clutch collar 49n'1ay beH mantainedlin, an vintermediate position whereby the clutch teeth 5|). and lkare all out of engagement Vwith. the clutch, teeth 26 and4l.

Immediately below the bearings 42, the .shaft 4I)y is provided with an .eccentric cam I55 which upon rota'tioritservesy to` reciprocatea plunger 56 againsta compression coil springr 5l. This plunger in combination fwith Vtheiball. valve. 58and seat 59 therefor .constitutesan ,oilr pump which ,serves to circulate lubricating oil4 around through various ducts 80 in the housing in order that thevarious bearings fand. gears `will be `at I.all times properly lubricated. f Inasrnuchfas this oil circulation 'system, forms .noVV partV of the. present invention, further description thereof is unnecessary. y y

The lowerY half offthemainfhousing is closed by means lof -a collar which .serves to'carry an--oil seal S8 yof conventional .construction -sur- .roundingthe shaft-49 and. -serves to 'enclose and seal thefhousing vin order T-tovv prevent' the entry -off dust 1 or, grit therein and-at thesaine time vpreventleakage-of .oil therefrom. l

As will be readily appreciated from the foregoing, the Ytaper shank= I9 may ccnvenientlybe connected toa suitablesourceof-power andduring. operation ofitheffapparatus this shafttmay `be Vconstantlyrotated. fRo'tationof the shaft I8 causes constant 'rotationrof theigear. cluster 3E about the countershaft .735 -anjdfcorresponding rotation of the idler gear 45--aboutitsjshaft-46- Inasmuch as-the idler '-gear-isinmeshing engagement with the-gear 4|.-whichfas-has `been ldescribed -above,-is journalledfor rotation about the shaft-A40, allofthesetgears will.l ha rotated constantlyas long asthe .tapershanl:.v I9 ist-rotated. -It isglikewfise vseen that` the, gears. 25-` and 4 |n rotate onf the ,sameV axisgbutin opposite ,directions, Consequentlyfit `wilL be appreciated-that when the collar '49"is: moved Aaxially -iipwaitdly essere along the upper splined portionof ,the.shaft..48, the clutch teeth I50 will'engage with the clutch teeth 26 and cause `driving.engagement between 'the` shaft 40and the shaft |8. Conversely,down ward .shifting of. the clutch collar49 will serve to establish driving engagement between .the clutch teeth and the clutch teeth 41 integrally formed on the upper axial face of the collar gear 4| thereby .establishing ,driving4 engagementbe-v. tween'the shaft 40 and the collar gear 4 4 *Y y u VIt will be seen that this downward shifting `of the clutch collar 49 will cause-V rotation lof the shaft lby the shaft i8. However, due tothe fact that the drive in this case is through the idler gear 45, rotation of theshaft 40 willfbe in a direction opposite fromthe direction of vrotaf tion of the shaft I8.

`The lower end of the shaft 40 is providedvwith i axially extending splines 10. These splines serve to drivingly engage a hollow internally vSplined` tap spindle 1| to permit axially downward movement of the tap spindle with respect tothe shaft 40 and at the Same time maintain a positive dri ing engagement therebetween. I y Y f nMounted in the lower collar 85 is a lead screw assembly which comprises` a split lead nut haV-. ing upper and lower portions i12 andk 13, each of which portions is internally threaded. `The, tap spindle 1l is externally threaded with suitable threads received between portions 12 and- .13 of 'the split lead nut, These portions 'l2 and 13 of the lead nut are locked against relative rotation with respect to each other by means of a dowel pin 14 and it is seen that this dowel pin extends into a suitable aperture inthe housing 65 and so serves the purpose ofpreventing rotation of the lead nut assembly with respect to the housing. n v

The lower portion of the housing collar 65 is externallyY threaded and receives a nut 16which cooperates with a lock nut collar11 which overlies the lower face of .the lower half .13 of the lead nut assembly. It is readily appreciated that by adjustment of the nuts 18 and 11, the separate portions 12 and 13 of the .lead nuty may be forced axially toward each other to taker up any backlash that may occur in the lead screw and nut assembly.

Y The lower end of the tap spindle 1| is provided with a conventional chuck assembly 18 which serves to provide easy and convenient means for mounting a tap 19. `f

From the foregoing description, it will be easilyv appreciated that when it is desired to tap a hole, a tap spindle having threads thereon corresponding to the lead of the thread ofthe tap to be used may .be assembled with a suitable corre-v control rod 83 mounted for vertical sliding moveapertures in.

merit in a .boss 84 and in suitable the housing proper. l

As is most clearly seen in Figure l, the upper end of the rod 83 is adapted to engage a laterally projecting stop member 85 carried by akvertically slidable rod 8B lmounted for vertical sliding move-k mentwithin the housing-x The rod 8,6' hasjsur# rounding the same-a compression' coil spring181- whichhas its upper lend abutting against'the Wall 'lof the housing and has its lower end abutting against ,aninwardly projecting fork which engages the clutch collar 49.V This spring 81 and rod 86,v therefore, normally tend to :force the clutch ycollar l49 downwardly `along the spline shaft 40 and tend at all times to cause the clutch teeth. 5| to engage with, the clutchteeth 41.

, Frompthe Vconstruction which is described, it will be apparent that' when the tap spindle has reached its downward limit of movement and the of the rod83. When the tapj spindle approaches its upperY extreme position of movement, the upper end ofthe rod 83 will engage the stop member 85. This engagement will cause an upward movement of the rod 86 againstthe action of the compression coil spring'8 .A -Y l 1 ,i

Upward movementQf the rod 86 will lcause a corresponding upwardmovement of the fork 88 and clutchcollar 49- associated therewith. Upwa-rd movement ofthe clutch collar'49 will cause a complete disengagement of the clutch teeth 5| and lthe Aclutch teeth 41 vthereby eliminating any further driving engagement between the shaft 40 and the tap spindle 1|. As soon as this disengagement takes place, 4the tap spindle will, `of

t course, cease 'rotation and, consequently, cease its-upward movement thereby discontinuing further upward movement of the rod 83. As a result of thiseonstruction, the -taper shank I9 and drive shaft I8 may continue to rotate, drivingthegear 25, copntershaft-SG, idler gear45'and collar'gear 4| without causing` any rotation whatsoever" of the shaft 40er tap spindle 1|. n l -The stop member-'la1soy is engaged on its underside by one end of' a lever95ym'ounted for pivotal movement on a suitable pin" 96. The upper side of the opposite end of this lever`v` is engaged by an arm 91 secured toxanarmature 98'v of a suitablesolenoicl 99. Current is supplied lto the solenoid from any suitable -sou'rce:f(notv shown) through a Amicro-switch |00 of' conventional construction. This switch is clearly illus` trated in Figure 2 of the drawings. The circuit to the solenoid'may be closed by depressingvthe'v button I 0|. This is accomplished by meansof' the exterior pushbutton |02 which engages al leafspring I 03 secured'tothe housing by suitable screws |04, the opposite end of the leaf spring engaging the plunger |0| which, when depressed, f

serves to close the circuit to the solenoid.

The switch |00 is of such construction'that when the plunger |0| is depressed the'circuit willA remain closed until the plunger |05 projecting from the opposite side ofthe switch |00 is depressed. 'Ihis plungerl |05 engages the exterior surface of a vertically slidable control rod |01' which is provided with a cam surface |08 thereon which, as is .clearly seenin Figure 2 of the drawings; serves to depress Kthe plunger |05 when the controlrod |01 ismoved downwardly." I

llF-has -surroundingits :upper-ends compression coilY spring m9 confined between agpin' H-extending through thel rod --and `the adjacent-wall of `'the housing in-which the Arod -l-l is slidaloly mounted.' rI'his compression-coil -springS-'convstantly tendslto urge the rod'l 01 upwardly. `'The rod L01 extends downwardly-.through the housing and is slidably mounted inthe boss '-8l which i serves also to provide-means-forslidably'mounting the follower rod 83. 'The rod ll'l has mounted thereon a stop member H2 which 'lies in the'pa-th of-movement .of astop collar- H3 secured to the rod 83' by meansof a set screw-IH.

From -the abovedescription, lit-will -be---elear thatin orderlto operate the tapping machine described above ,the plunger m2 may be manually depressed .by the operator. -Depressing f this plunger will, through themediurn of the-leaf spring m3, vdepress .the plungerll closing the circuitof the solenoid399. The energizing of this ing. engagement'between the clutch teeth-50 and the clutch teeth 26. Engagement of these clutch teeth establishes `a Vdirect driving engage-ment between the shaft' i8: and the shaft'wandcauses theA shaftzzd to :be rotated by the shaft -I8 inj the same directionfas 'the rotation-of the shaft -l-8. Inasmuch as the tap spindle 1 I is drivingly interconnected by means of the splines/10 tothe lower end of the .shaftl0-,. this driving connection will cause forward. rotation of the tap spindlefl l.

"Duel tothe engagement between the `threads onv the exterior-surface of the tap spindle andthe threadsv othelead nut assembly-,i-rotationof the tap Vspindle in this forward direction will cause the tap spindle to be .-fed downwardly toward the Workv atfa rate commensurate with the :lleadofV the particulartap forwhich the `lead screw -assembly zwas designed. This. downward feed 'of the tap and ltap spindle- .will obviously.y continue untilthe Ytap spindle' has reached a predetermined desired depth: -of cut. `"li-his .deptlrof-f'cut is controlled by theadjustable .collar vB3-adjustably.securedl to the--shaitiiby meanso the set screw lll.

1in: View of thefact .thatzthe forkll and. rod-83 are carried downwardly with Vthe tapl spindle, l'the rod83 will move downwardlyfwitii the .tap spindle noid 99;y and cle-energizing..the` same. When thel solenoid .193i iside-energ-ized,1the compression-.coil spring 51 :will-'gforce-.the roda-6 -downwardiy.- and' force-the' righthand. endiiofthavleven '95 vr.downwardly thereby-raising the armature ofthe solemnd toi-its:-orlginarpition.' 'At". thezsaniatime,

downwardrmovement 'of gtlie vrod' will causel a corresponding ydownward movement of 'the' fork 88 and' its vassociated clutch collard'disengaging the clutch teeth' fromthe clutchteetliZl and forcing the clutch/teeth `5f into engagement with the clutch'teethfl.

downwardmovement of'the clutch, as 'has beendescribed above,-will now establish a driving engagementbet-ween the shaft I8 and the lshaft 40 throughthe 'gear clusteril, idler gear 45,'and collar gear 4l-'thereby causing the shaft 40 torotate in thereversedirection or, rather, in ra 'direction opposite to the directionof rotationof the shaft-JH. This reversal ofthe direction of drive ofthe tap'spindle will cause the tap spindle toc-move upwardly `andas -it moyesfu-pwardly, it will cause a corresponding upward-"movementof thefrod-83- -As has been -described above, vwhen the-rod -83- approaches the upper end of its -movement, its-upperend 'will -en-gagethe stop Ymember and .intended for tapping extremely -deep holes or for usein a .tapping operation where the length ofthe axialmovement--of' .the tap. spindle isfconsiderably greater than is normally required. -In this `form oftheinivention, .a modified .form-of lowercollarassemlbly- .420 isemployed which lower collar .is .provided..fwith .outwardly -ex-tending bosses |221 .carrying bearings .1.22 mounted for axial sliding-movement. in the bearings |22 and shafts 123 whichiare; anchoredV toa follower plate 4.24 inwhieh the.- lower portion of the. tap spindle isK journalied forfrotation inlany.-l suitable. fashion;

Alhisconstruction provides an: outboard. support furthe tap spindle when the-.same is ex.- tended beyond` the range of -movementrequired iny a `normal. tapping, operation. .As .is clearly seen -in-Figure'L. this .construction permits the elimination of the fork 8| andtheicontrolv rod .83 may vlnefbolted directly to a suitable. projection I-Z-oni the. follower.V plateli24. In other respects, ther-constructionof. this. modied form of tap.- pilhead may be substantiallyas .describedaboye inionnection ,with the.- preferrediorm of thel in Ve ien.

1-lg-ure-rk ll isral` diagrammatic view of .apircuit Dycmrls 0f. ll-.hihi-a-,1p1li113a1ityof tapping heads or tapping machines. may be simultaneously operated. The peculiar. advantage of `this assembly embodying tapping; headsv or machines of. the typegherein described resides in the factthat-a pluralitynfl holes -otdift'erent depths and having `different pitch threadsmay simultaneously be tapped if .desired inasmuch as each tapping. head or machinek .operates entirelyindependently ofj each ofthe .others and operates substantially automatically once its cycle of operation haslbeen' started.

inthe `circuit diagram, 130 represents one side positeside. Y -A master switch UI 32 may serve: to

energ-iZe--a-masterrelay P33. This master relay ascenso Similarly, closing of secondary relay |43, closing the switch |44 and energizing the -solenoid |45, It will be seen that, as a result of this construction, closure of the master switchv |32 will serve to set into operation a plurality of tapping heads. Each of the tapping heads will automatically be fed downwardly to tap the hole required to the predetermined depth 'for which that particular tapping head may be set. In each instance, when the predetermined depth of hole'has Ibeen reached, each individual tapping head will reverse its direction of travel and return to its original position entirely independently of the operation of the remaining tapping heads in the circuit. This construction is particularly advantageous where it is desired to perform several tapping operations on a single workpiece wherein the holes tobe tapped may be of entirely different depth and different pitch threads, yet at the same time the entireftapping operation of all holes necessary may be accomplished simultaneously.

As has hereinbefore .been pointed out, the above description and disclosure of the drawings relates solely to a tapping head construction adapted for attachment to a drill press, turret lathe, or other machine tool. It will, however, 'be obvious to lthose skilled in the art that a great many of the novel features and important improvements herein disclosed may equally well be embodied in a machine designed and built solely for the purpose of tapping holes. The invention herein disclosed, therefore, contemplates the inclusion not only yof the novel and specific features described above, but also contemplates substantial modifications thereof falling within the scope of the invention as defined in the following claims.

What is claimed is:

l. In a device for tapping threads including a drive shaft, an axially reciproca-ble lead. screw controlled tap spindle, reversing gearing and axially shiftable clutch means serving to interconnect said drive shaft with said tap spindle either being hollow and internally splined throughout at least a portion of its length, and an externally splined shaft for driving said tap `spindle telescoping therein. f

4. A tapping. machine vconstructioncomprising in combination,'a drive shaft, a tap spindle, a reversing gear assembly, clutch means serving to drivingly interconnect said drive shaft with said tap spindle either direct or through said reversing gear assembly, and meansincluding a rod movable with said tap spindle for actuating said clutch means in accordance" with thefaxialposi.-` tion of said tap spindle.

5. In a tapping machine having a drive shaft,A

a tap spindle and reversing gearing', an axially shiftable clutch serving to establish a driving connection between said shaft and spindle either directly therebetween or through said reversing mechanism, a solenoid serving to effect axial movement of said clutch in one direction and an axially shiftable control rod associated with said tap spindle serving to effect axial shifting of said clutch in the opposite direction.

6. A tapping machine construction including a housing, aldrive shaft journalled for rotation in said housing, clutch teeth on one axial face of said drive shaft, an intermediate shaft coaxially arranged with respect to said drive shaft, a tap spindle splined to said intermediate shaft for rotation therewith and for axial movement with respect thereto, a collar rotatable on and coaxially arranged with respect to said intermediate i shaft, reversing gearing drivingly interconnectdirectly or through said reversing gearing, a control rod interconnected with said tap spindle for axial movement therewith, and means interconnecting said control rod with said clutch mechanism whereby to actuate said clutch in accordance with the axial position of said tap spindle.

2. Tapping apparatus, including in combination, a drive shaft, a tap spindle, reversing gearing, axially shiftable clutch mechanism serving to establish a driving connection between said4 3. In a tapping machine construction, a tap` spindle including a chuck for mounting a tap therein, said spindle being externally threaded.

said thread having a lead corresponding to the lead of the thread of the tap, said tap spindle ing said collar and said drive shaft to drive the same in a direction opposite to the direction of rotationof said drive shaft, clutch teeth on one axial face of said collar and an axially shiftable clutch member slidable on and drivingly interconnected with said intermediate shaft and having a series of 'clutch teeth on each of the axial faces thereof, one set of said clutch teeth being adapted to engage the clutch teeth on the axial face of said drive shaft and the other set of clutch teeth being adapted to engage the clutch teeth on the axial Iface of said collar.

7. A tapping machine construction including a housing, a drive shaft journalled for rotation in said housing, clutch teeth on one axial face of said drive shaft, an intermediate shaft coaxially arranged with respect to said drive shaft, a tap spindle splined to said intermediate shaft for rotation vtherewith and for axial movement with respect thereto, afcollar rotatable on and coaxially-arranged with respect to said intermediate shaft, reversing gearing drivingly interconnecting said collar and said drive shaft to drive the same in a direction opposite to the direction of rotation of said drive shaft, clutch teeth on one axial face of said collar, an axially shiftable clutch collar slidable on and drivingly interconnectedwith said intermediate shaft and having a series of clutch teeth on each of the axial faces thereof, one set of said clutch teeth being adapted to engage the clutch teeth on the axial face of said drive shaft and the other set of clutch teeth being adapted to engage the clutch teeth on the axial face of s aidcollar, a fork for axially v shifting said clutch collar, and means interconnecting said tap spindle and fork serving to shift said clutch collar when said tap spindle has reached a predetermined axial position.

8. A tapping machine construction including a housing, a drive shaft journalled for rotation in said housing, clutch teeth on one axial face of said drive shaft, an intermediate shaft coaxially ingr afseriesof clutchteethioneachoffthe axial faces thereof, one set of said clutch teeth being adapted to engage'the clutch-teeth on 'the-axial face of said. drive'` shaft and the lathen set` of clutch` teeth being adapted to engage theclutch teeth-Joni the axial `face of said collar; a.V fork 'for axially shifting-said clutch co1Iar,a` control rod operatively connected'tosaid tap spindle and movabie'axially" therewith, and'means on said control rodadapted toengage' said fork whereby to effect vshiiting'of said clutch collar when said tap spindle-'reaches a predetermined axial position( SVEN B'.v HELLSTROM; 

